The present invention relates to modification to a vertical interconnect access (VIA) of a printed circuit board to mitigate or eliminate signal integrity degradation caused by a conductive stub. More specifically, the invention relates to back-drilling the VIA to create a countersunk VIA channel.
In a printed circuit board (PCB), a VIA is a conducting channel between two or more substrate layers to make signal connections between different layers of the PCB. If the connection formed by a VIA is near one surface of the PCB, then the part of the VIA extending away from the connection to the opposite surface of the PCB forms a stub, which can cause a deterioration in signal integrity. Back-drilling is a process to remove the stub to improve signal integrity.